The present invention relates to switchgear, in particular relays and/or contactors with a solenoid system that includes an armature and a yoke, a coil and an open- or closed-loop controller of the switchgear drive, wherein actual values of drive-specific switching parameters are measured by sensors.
Switchgear having solenoid systems, for example, contactors, are used in drive and automation technology and serve, in conjunction with other components, for protecting and controlling electric loads.
In order to optimize such switchgear to their switching function, taking into consideration different operating conditions and specific equipment characteristics, the principle of controlled switching drives has been developed, which reduces the number of types of coils that were previously required due to their different excitation voltages. Such drives can be used for both AC and DC and, by reducing contact chatter, they reduce contact erosion and extend contact life. At the same time, the power consumption of the exciter circuit during the holding phase is reduced.
Thus, European Patent Application 376 493 describes a control circuit that allows for a high current during the closing operation of electromagnetic valves; this current is then reduced to a relatively holding current after the closing operation. German Patent No. 30 47 488 A1 describes, in addition to a coil current controller, an induction controller having a Hall probe arranged in the yoke. These control principles provide a higher coil current for the closing operation, which is reduced after the closing operation to a value that just provides for the force required for holding the armature in the closed position. German Patent No. 44 30 867 describes a switchgear drive control, which ensures that the optimum contact speeds and the limitation of the armature core impact speed are observed over the entire service life, taking into consideration interfering factors such as erosion and tolerances.
While efforts have de to achieve the aforementioned object using the correctional circuit arrangements for switchgear drives, either complex control algorithms have had to be used or concessions concerning the requirements of high closing speed of the contact with minimized chatter and low power consumption during the holding phase of the contactor have had to be made.
An object of the present invention is to provide a simple and sturdy control algorithm of the switchgear drive resulting in high contact closing speed and minimum chatter of these contacts and low power consumption of the exciter circuit during the holding phase of the contactor.
This object is achieved according to the present invention by the fact that, after a switching command, the control device does not affect an output quantity, for example, coil current I, until at least one predefined threshold value of the switching parameters, for example, contact speed and/or this contact path and/or the flux is attained during a switching operation.
Thus it is achieved that the closing speed is very high, like in conventional contactor drives. After one or more limit values of specific switching parameters has been attained, such as time or contact path, the control device intervenes via flux or coil current I and thus minimizes chatter. In addition, power consumption by the exciter circuit during the holding phase of the contactor is thus reduced. These threshold values can be transmitted to the control device via sensors. Lag elements in the control circuit also result in delayed response of the control device.